/**
* Verify that some non-looping paths from {@code a} to {@code b} pass through at least one node
* where {@code nodePredicate} is true.
*/
private boolean checkSomePathsWithoutBackEdges(DiGraphNode<N, E> a, DiGraphNode<N, E> b) {
if (nodePredicate.apply(a.getValue()) && (inclusive || (a != start && a != end))) {
return true;
}
if (a == b) {
return false;
}
for (DiGraphEdge<N, E> e : a.getOutEdges()) {
// Once we visited that edge once, we no longer need to
// re-visit it again.
if (e.getAnnotation() == VISITED_EDGE) {
continue;
}
e.setAnnotation(VISITED_EDGE);
if (ignoreEdge(e)) {
continue;
}
if (e.getAnnotation() == BACK_EDGE) {
continue;
}
DiGraphNode<N, E> next = e.getDestination();
if (checkSomePathsWithoutBackEdges(next, b)) {
return true;
}
}
return false;
}
private void discoverBackEdges(DiGraphNode<N, E> u) {
u.setAnnotation(GRAY);
for (DiGraphEdge<N, E> e : u.getOutEdges()) {
if (ignoreEdge(e)) {
continue;
}
DiGraphNode<N, E> v = e.getDestination();
if (v.getAnnotation() == WHITE) {
discoverBackEdges(v);
} else if (v.getAnnotation() == GRAY) {
e.setAnnotation(BACK_EDGE);
}
}
u.setAnnotation(BLACK);
}